1. Field of Invention
The present invention relates to a pump for inflating and deflating.
2. Related Prior Art
U.S. Pat. No. 6,422,832 discloses an air pump capable of inflating and deflating an inflatable object interchangeably. This air pump includes a main body or cylinder 10 defining a duct 11, a base 21, an air-discharging tube 23, an air-admitting tube 24, an adjustment member 40 and a hose 50. The cylinder 10 defines four holes 15˜18 communicated with the duct 11. The base 21 includes a first connecting port 211, a second connecting port 212, a first manifold 214 communicated with the first connecting port 211 and a second manifold 215 communicated with the second connecting port 212. Through the hole 15, the cylinder 10 is communicated with the first connecting port 211. In the hole 15 is installed a check valve 25 for directing air from the cylinder 10 to the base 21 only. The first manifold 214 is communicated with a lower end of the air-discharging tube 23. Through the hole 17, the cylinder 10 is communicated with an upper end of the air-discharging tube 23. In the hole 17 is installed a check valve 27 for directing air from the cylinder 10 to the air-discharging tube 23 only. Through the hole 16, the cylinder 10 is communicated with the second connecting port 212. In the hole 16 is installed a check valve 26 for directing air from the base 21 to the cylinder 10 only. Through the hole 18, the cylinder 10 is communicated with an upper end of the air-admitting tube 24. In the hole 18 is installed a check valve 28 for directing air from the air-admitting tube 24 to the cylinder 10 only. The adjustment member 40 is rotationally mounted on the base 21. The adjustment member 40 defines a first opening 41 and a second opening 42 communicated with the first opening 41. The first opening 41 of the adjustment member 40 is selectively communicated with the first connecting port 211 or the second connecting port 212. The second opening 42 of the adjustment member 40 is communicated with the hose 50. Referring to FIGS. 2, 4 and 5 of U.S. Pat. No. 6,422,832, the openings 41 and 42 of the adjustment member 40 are communicated with the first connecting port 211 of the base 20. Referring to FIG. 4 of U.S. Pat. No. 6,422,832, when a piston 31 is moved downward in the cylinder 10, air is pumped from the cylinder 10 to the hose 20 through the hole 15 of the cylinder 10 and the first connecting port 211 of the base 21. Referring to FIG. 5 of U.S. Pat. No. 6,422,832, as the piston 31 is moved upward in the cylinder 10, air is pumped from the cylinder 10 to the hose 20 through the hole 15 of the cylinder 10 and the first connecting port 211 of the base 21. Referring to FIGS. 6˜8 of U.S. Pat. No. 6,422,832, the openings 41 and 42 of the adjustment member 40 are communicated with the second connecting port 212 of the base 20. Referring to FIG. 7 of U.S. Pat. No. 6,422,832, as the piston 31 is moved downward in the cylinder 10, air is sucked from the hose 20 to the cylinder 10 through the second connecting port 212 of the base 21 and the hole 18 of the cylinder 10. Referring to FIG. 8 of U.S. Pat. No. 6,422,832, as the piston 31 is moved upward in the cylinder 10, air is sucked from the hose 20 to the cylinder 10 through the hole 16 of the cylinder 10 and the second connecting port 212 of the base 21. However, the inclusion of the tubes 23 and 24 increases the volume of the pump. The inclusion of the four check valves 25˜28 increases the cost of the pump. The rotation of the adjustment member 40 on the base 21 interferes with installment of the pump in a limited space. The angular position of the adjustment member 40 on the base 21 cannot be locked, and unintentional rotation of the adjustment member 40 on the base 21 hinders the operation of the pump.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in the prior art.